package demo;

import java.util.LinkedList;
import java.util.Queue;

class MyStack {
    private Queue<Integer> qu1;
    private Queue<Integer>qu2;

    public MyStack() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();

    }
    //入栈
    //入到不为空的队列中 如果都为空 入到qu1
    public void push(int x) {
        if(!qu1.isEmpty()){
            qu1.offer(x);
        }else if(! qu2.isEmpty()){
            qu2.offer(x);
        }else{
            qu1.offer(x);
        }
    }

    public int pop() {
        if(empty()){
            return -1;// 两个队列都为空，栈为空
        }
        if(!qu1.isEmpty()){
            int size = qu1.size();
            for(int i = 0; i < size-1; i++){
                int tmp = qu1.poll();
                qu2.offer(tmp);
            }
            return qu1.poll();
        }else{
            int size = qu2.size();//每弹出一个就会减少一个 需把size从for中拿出 定义一个常量
            for(int i = 0; i < size-1; i++){
                int tmp = qu2.poll();
                qu1.offer(tmp);
            }
            return qu2.poll();
        }

    }

    public int top() {
        if(empty()) {
            return -1;//栈为空的
        }
        int tmp = -1;
        if(!qu1.isEmpty()) {
            int size = qu1.size();
            for (int i = 0; i < size; i++) {
                tmp = qu1.poll();
                qu2.offer(tmp);
            }
            return tmp;
        }else {
            int size = qu2.size();
            for (int i = 0; i < size; i++) {
                tmp = qu2.poll();
                qu1.offer(tmp);
            }
            return tmp;
        }
    }

    public boolean empty() {
        //两个队列都为空时
        return qu1.isEmpty() && qu2.isEmpty();
    }
}
